Feb 12-13 Sleet/Snow/ZR Event

[SnowNiner]

So what do we look for on the models for a stronger High?  What would keep it stronger and in place longer? 

[Wow]

So what do we look for on the models for a stronger High?  What would keep it stronger and in place longer?

More of a 50/50 low signature that will keep the high from moving out to sea.

[ncskywarn]

Can someone provide a link for these charts?  I used to have it, but can't find it now.  Thanks!

http://coolwx.com/cgi-bin/getbufr.cgi?region=NC&stn=KRDU&model=gfs&time=current&field=prec

[packfan98]

http://coolwx.com/cgi-bin/getbufr.cgi?region=NC&stn=KRDU&model=gfs&time=current&field=prec

Thanks!

[SnowNiner]

More of a 50/50 low signature that will keep the high from moving out to sea.

 

Great, thanks. 

[Spidyr2k]

How much influence provided by extensive snow pack just to our north, and how well do the globals compensate for it? TIA.

[rduwx]

Of course my cmc is stuck at hr 144 but looks encouraging.  1032 high to the north w/ moisture on it's way.  Anybody have more details on where it went from there?

[superjames1992]

The 12z GGEM looks pretty amped/inland.  It's still a major ice (sleet?) storm for the CAD regions after an initial burst of snow, but the surface low tracks up to northern AL by hr 156 and is just offshore of the Delmarva Peninsula by hr 168.  It also shoots out a little bit of precip in the form of snow around 108-120 for NC/TN.  Not sure I buy that track with a strong HP to the north, but we'll see.  Am I correct when I say the Canadian has the tendency to get a little more amped than is reality?  I know it's shown quite a few fantasy storms this year out of nowhere.

 

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And the 12z UKMET comes in suppressed, as we'd all expect.  There's a decent high in damming position with a 1011 mb LP a couple hundred miles south of Mobile at hr 144 (the end of its run).  I think this is a good sign as we'd expect the UKMET to be more suppressed than the other modeling.

 

[LithiaWx]

Many portions of NC look golden for a big froEn precip event. For GA the setup is there for ZR but the models don't agree at the surface.

[BIG FROSTY]

GFS gives me .72qpf  850s run -2.5 to +1.6 at the end.

[rduwx]

The 12z GGEM looks pretty amped/inland.  It's still a major ice storm for the CAD regions after an initial burst of snow, but the surface low tracks up to northern AL by hr 156 and is just offshore of the Delmarva Peninsula by hr 168.  It also shoots out a little bit of precip in the form of snow around 108-120 for NC/TN.  Not sure I buy that track with a strong HP to the north, but we'll see.  Am I correct when I say the Canadian has the tendency to get a little more amped that is reality?  I know it's shown quite a few fantasy storms this year out of nowhere.

 

Thanks James!

[GaWx]

Now, we have 11 of the last 12 GFS runs and the last 4 Euro runs with at least a good portion of NC getting significant wintry precip. within 2/11-13. I want to keep this tally going because it is IMO a good indicator of the chances this will actually materialize. Also, I feel it is good for record keeping of the models' performance after the fact, which may help establish confidence levels for forecasting future threats.

Verbatim per my provider's maps, practically all of N GA stays above 32 through the event. However, considering the almost textbook setup of Miller A, cold high (lows near 10 NYC inland burbs and N NJ), decent strength high (1032 mb 12z on 2/12), a pronounced wedge, surface temp.'s in the high 30's all of the way down to Montgomery and Columbus, 850's stuck in the critical +3 to +4 C range for major ZR, and heavy amounts of qpf (a whopping 1 to 1.5"), I sincerely feel the modeled surface temp .'s for N GA are quite possibly, if not likely, too warm by several degrees (as alluded to by Lookout). If that is really the case, we could easily be looking at the worst ZR for the ATL-AHN corridor and surrounding areas since at least 1/2005. I mean this run is almost textbook for major N GA ZR. Also, the ENSO being neutral negative is more supportive of major ZR there than any other ENSO phase per history fwiw.

I just looked at MeteoStar. It has it getting down to 35 on ATL's southside, 34 on ATL's northside, and 33 at Athens during a large portion of the precip. This is the coldest GFS run yet for that corridor and is very close/about as close as can be to major ZR there verbatim. Based on the things I mentioned in the post just before this, I now think that this as modeled on the 12Z GFS is likely a major ZR for the ATL-AHN corridor. Keep in mind that I have studied numerous wx maps for past events in helping me to conclude this. So, I'm saying I believe that the model's sfc temp.'s are several degrees too warm and that this would be a major ZR in reality IF this run's 850's/surface features were to happen to verify pretty closely. Now, I'm, of course, not predicting a major ZR there as of now. However, I am saying that that is very much on the table as a reasonable possibility for the N GA CAD areas/ATL-AHN corridor as supported by this run. This is about as textbook a look as you'll find IMO.

[JoshM]

KCLT showing little over an inch of ZR and about an inch of snow

[Tacoma]

How much influence provided by extensive snow pack just to our north, and how well do the globals compensate for it? TIA.

I've often heard a good snow pack to the north of us would help our chances to keep cold front from modifying and would also help in keeping it cold enough for snow.

[Hammer]

I just looked at MeteoStar. It has it getting down to 35 on ATL's southside, 34 on ATL's northside, and 33 at Athens during a large portion of the precip. This is the coldest GFS run yet for that corridor and is very close/about as close as can be to major ZR there verbatim. Based on the things I mentioned in the post just before this, I now think that this as modeled on the 12Z GFS is likely a major ZR for the ATL-AHN corridor. Keep in mind that I have studied numerous wx maps for past events in helping me to conclude this. So, I'm saying I believe that the model's sfc temp.'s are several degrees too warm and that this would be a major ZR in reality IF this run's 850's/surface features were to happen to verify pretty closely. Now, I'm, of course, not predicting a major ZR there as of now. However, I am saying that that is very much on the table as a reasonable possibility for the N GA CAD areas/ATL-AHN corridor as supported by this run. This is about as textbook a look as you'll find IMO.

I agree with you on the surface temps (having read all of your postings on historical data, etc.), and esp. worry about those of us in the northern burbs.  Add in that I am supposed to be flying back to ATL on Thursday... not having a good feeling about that...

[Cold Rain]

If this will truly be a Miller A storm, I would not expect a wide zone of ZR, regardless of what the models might be showing now.

[Wow]

If this will truly be a Miller A storm, I would not expect a wide zone of ZR, regardless of what the models might be showing now.

Yes, historically Miller A storms will only have a narrow band of ice and are primarily a rain or snow event.

[packfan98]

If this will truly be a Miller A storm, I would not expect a wide zone of ZR, regardless of what the models might be showing now.

You are right.  Traditionally Miller A storms are either snow or rain.  From what I can tell about the GEFS, the track of the low looks really favorable for a good SE storm.  Low pressure shows up on the Atlantic Coast of Florida and rides all the way up the eastern seaboard.  The big negative I see is that there is a strong low scooting across the Great Lakes region that's pushing out our High pressure and cold air.

[FallsLake]

Yes, historically Miller A storms will only have a narrow band of ice and are primarily a rain or snow event.

This begs the question if it's a Miller A would there be more cold air available north and west of the storm?  

[packfan98]

This begs the question if it's a Miller A would there be more cold air available north and west of the storm?  

Not if there is a low in the Great Lakes region.  See my last post.

[rduwx]

You are right.  Traditionally Miller A storms are either snow or rain.  From what I can tell about the GEFS, the track of the low looks really favorable for a good SE storm.  Low pressure shows up on the Atlantic Coast of Florida and rides all the way up the eastern seaboard.  The big negative I see is that there is a strong low scooting across the Great Lakes region that's pushing out our High pressure and cold air.

 

That seems to be a constant thing over the past 2 years...LOL.

[SnowNiner]

Thats a good point. Miller a s really are usually rain or snow. Its also a good point about that lakes low up north. How have they been modeled this winter? The cold air may be up to how much that interferes with our confluence. Hopefully it disappears.

[GaWx]

If this will truly be a Miller A storm, I would not expect a wide zone of ZR, regardless of what the models might be showing now.

 

 I don't disagree and I realize your comments are not aimed toward N GA, specifically. However, for ATL (I'm not talking about NC climo, which isn't the same), there have been a respectable 7 major ZR's involving a Miller A (that's about 25% of them; anyone interested could look up the old wx maps if they want as that is obviously how I discovered this), including the great 1/1973 ZR:

 

- 2/6-7/1979

- 1/7-8/1973 (one of the worst, if not the worst, in ATL on record)

- 3/25/1971

- 12/25/1943

- 1/7/1940

- 12/16/1932

- 1/21/1918

 

 All seven of these had similar tracks of the Miller A low.

[BullCityWx]

Looking at the sounding for Gastonia, I'd expect more IP than ZR there. There is only one layer above freezing and it's only around 1C. Almost cold enough to be an isothermal layer. As a matter of fact, I'd bet on the bulk of that precip to fall as either SN or IP in Gastonia and Charlotte IF the sounding remains the same. It isnt until hour 153 where it truly looks like a ZR sounding.

[Cold Rain]

 

You are right.  Traditionally Miller A storms are either snow or rain.  From what I can tell about the GEFS, the track of the low looks really favorable for a good SE storm.  Low pressure shows up on the Atlantic Coast of Florida and rides all the way up the eastern seaboard.  The big negative I see is that there is a strong low scooting across the Great Lakes region that's pushing out our High pressure and cold air.

 

You posted the Ens Mean and it shows exactly what you described....the Snow Blocker showing up around the Lakes as the system moves in. On the operational (below) that feature isn't so much the key driver of potential cold air issues. A bunch of precip has fallen by the time it comes into play. The issue on the Op is the confluence zone migrating to the east, or the storm coming in too slowly or both (take your pick). This is very evident between 144 (top) and 156 (bottom).

Since there is no blocking (read -NAO) to hold the 50/50 type feature in place, it continues to slide east, pulling the best confluence with it. Thus, HP slides out leaving an insitu situation. The result is, we get lucky (or unlucky, depending on your point of view) that a bunch of precipitation falls as frozen before it changes to rain. The High hangs around JUST long enough to allow a significant winter storm.

The GFS verbatim is a tightrope.

[SN_Lover]

Thats a good point. Miller a s really are usually rain or snow. Its also a good point about that lakes low up north. How have they been modeled this winter? The cold air may be up to how much that interferes with our confluence. Hopefully it disappears.

The warm nose with this event is quite staggering. It will be a race between how quick the moisture comes in by the time the inversion erodes. 

 

[GaWx]

 I don't disagree and I realize your comments are not aimed toward N GA, specifically. However, for ATL (I'm not talking about NC climo, which isn't the same), there have been a respectable 7 major ZR's involving a Miller A (that's about 25% of them; anyone interested could look up the old wx maps if they want as that is obviously how I discovered this), including the great 1/1973 ZR:

 

- 2/6-7/1979

- 1/7-8/1973 (one of the worst, if not the worst, in ATL on record)

- 3/25/1971

- 12/25/1943

- 1/7/1940

- 12/16/1932

- 1/21/1918

 

 All seven of these had similar tracks of the Miller A low.

 

 I also want to add that the great Feb. of 1979 sleetstorm that gave ATL ~4" (their greatest IP in decades) was also from a Miller A. 

[Snowless in Carrollton]

I don't disagree and I realize your comments are not aimed toward N GA, specifically. However, for ATL (I'm not talking about NC climo, which isn't the same), there have been a respectable 7 major ZR's involving a Miller A (that's about 25% of them; anyone interested could look up the old wx maps if they want as that is obviously how I discovered this), including the great 1/1973 ZR:

- 2/6-7/1979

- 1/7-8/1973 (one of the worst, if not the worst, in ATL on record)

- 3/25/1971

- 12/25/1943

- 1/7/1940

- 12/16/1932

- 1/21/1918

All seven of these had similar tracks of the Miller A low.

I can't get over that major zr at the end of March. It's also interesting that there hadn't been a major zr involving a miller a in 35 years !

[burgertime]

Euro is a big hit for I 40 and almost a huge hit for CAD areas

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[GaWx]

 The 12z Euro is the 5th in a row with a major winter storm for part of the SE within 2/11-13. Add that to 11 of the last 12 GFS runs.